1. Field of the Invention
The invention relates to connectors, and more specifically to “RF” coaxial connectors for high frequency systems.
2. Description of the Related Art
RF connectors are the forgotten component of microwave systems even though they have been in use for 100 years or so. Many design engineers consider them as an after thought, yet without a properly designed connector many of today's systems would not have been realized. nor would they have worked.
Initially, there were minimal performance parameters associated with these devices. During WWII, the emerging radar technology gave rise to the need for frequency-dependent performance parameters. During this time, Paul Neill, an engineer at Bell Labs, is credited with developing the first performance driven connector, the type “N”. (The type N is a threaded air dielectric interface connector which is still used today.) Shortly after the development of the N connector, Karl Concelman, an engineer at IPC (the predecessor of Amphenol RF) is credited with the type “C” development. The C is a bayonet coupled connector with a Teflon dielectric interface. With these 2 connectors, many of the current commonly used connectors were derived. The BNC (Bayonet-Neill-Concelman) became the industry workhorse. The BNC connector today, besides its original 50 ohm configuration, has a 0.75 ohm version widely used in the telecommunications industry. The development of the TNC (a threaded BNC) is credited to General RF Fittings (GRFF), the predecessor of SV Microwave, the assignee of the instant invention.
A conventional BNC connector, as used in consumer electronics, communications systems, and widely in the broadcast industry, is shown in FIG. 1. The end of a coaxial cable is fitted into main body 1 and is connectable to a female receptacle (not shown) via bayonet sleeve 2. Contact 7 mates with a corresponding contact in the female receptacle, and outer conductor 3 mates with a corresponding outer conductor in the receptacle. A pin in the female receptacle engages the ramped circumferential groove in bayonet sleeve 2; when bayonet sleeve 2 is rotated, the female pin rides along the ramped groove, and the receptacle and the bayonet sleeve (and thus the BNC connector) are pulled together snugly. Spring washer 4 is fitted within the rear portion of bayonet sleeve 2 and has a concave shape. Spring washer 4 serves to provide some biasing force to bayonet sleeve 2.
The conventional BNC connector of FIG. 1 performs acceptably in traditional applications. However, in modem higher frequency applications, the conventional BNC connector is inadequate. The conventional BNC connector suffers from poor stability between the bayonet sleeve and the main body. The bayonet sleeve is loosely secured to the main body and has the ability to jiggle radially and can cant at an angle to the longitudinal axis of the connector. At lower frequencies, this loose fitting is acceptable because the signal is unaffected. However, as the frequency increases, the signal degrades; signal reflections may occur, clock signals may be ramped, or transmission of the signal may be lost entirely. Although the prior art BNC connector is rated by the manufacturer for signals of up to 4 GHz, it is not practically usable at frequencies above 2 GHz.
As mentioned above, another connector that is available is the TNC connector. In such a connector, the bayonet sleeve is replaced by a threaded coupling which facilitates the attachment to its mating receptacle. While the TNC connector is more secure and stable than the standard BNC connector, it is unwieldy to use. It is a relatively slow and time consuming process to manipulate the threads on the coupling sleeve. This is especially problematic in most modem telecommunications or broadcast applications, in which a person may have to secure tens or hundreds of connections at a time.
Thus, there is a long-felt need for an RF connector that is suitably stable for high frequency applications, e.g., in the range above 2 GHz, that is easy, secure, and quick to connect or disconnect.